This mod replaces the dogs G-Mutations Ivy zombies & Mr.X (s) with zombies.It works for the STEAM retail version of the game.I tried to replace the lickers but it made the zombies walk on the ceiling ! but I found a way to remove the lickers completely (theres only like 4 lickers in 4th Survivor mode anyway).& I didnt replace Birkin or The Tyrant (s).I only use this mod for 4th Survivor mode if you use it for story mode some cutscenes or other stuff may be weird...